Shore Thing

Ok, so i had a gen V 454 mag carb w/gil exhaust in the boat. engine is frozen.

Now i'm going to replace it with a 502 short block carb.
(some friends are gonna build it for me as i know nothing)

Question 1:
What, if anything can I transfer from the 454 to the 502

Question 2:
buy a GM crate motor or something from 1800runsnew or similar shop?

Question 3:
Want to make around 500hp. What components should i use to build it? Keeping in mind, I want to buy quality, but i don't have to have the very top of the line stuff. Most important thing is that I want it to be RELIABLE.

Question 4:
Any additional recommendations or lessons learned?

Thanks guys. This is going to be a huge learning experience for me, but i want to do it right the first time.

-Lance

Whiteknuckle

Century,
A couple of suggestions. If you know nothing about this and you want ultra reliable, don't have "your friends" build your engine. They will not be your friends after the project is complete. There are many good marine engine builders out there that can give you what you want, when you want it, and in the long run with everything considered, it will be cheaper than having your friends build it.

500 HP is very common and not that challenging from a 502, But don't rush into this, do your homework, and get started on the right foot. Go to an experienced builder that will custom your engine to your boat and the way you use it and will guarantee his work. Listen to what I am saying!

Shore Thing

Whiteknuckle,

I understand completely what you are saying about the friend thing. However, i do have a constraint. I have the cash to purchase the parts but not hell of a lot more. The two friends of mine who are going to build are going to do the whole thing from removing my old engine to building and water testing the new one for $500. Of course i'd rather have a professional builder do it, but the cost is huge. The good news is that these two friends of mine built 4 very similar engines last year. for their own boats plus one the year before for another friends boat. I'm not saying its a perfect situation, but for the $$ i have to spend on this project, i think they are probably the best option. Keep em coming!! thanks.

BY U BOY

Get A Zz502 500hp From Gm.
You Can Use Pretty Much All The Accessories From The 454.

WHATS WRONG WITH THE 454?

Shore Thing

I haven't pulled it out of the boat yet, but we've pulled all the spark plugs and found salt water in one of the cylinders. Engine won't turn over even with a breaker bar. Gonna get it out of the boat and then really assess its condition. Either way, I want more power and the 502 is the best way to get it.

Is the zz502 intended for marine use? I've been looking at prices on them and keep seeing conflictings disclaimers. some say not intended, some say ok for marine use.

BY U BOY

THERE ARE A FEW GUYS HERE THAT ARE RUNNING THEM AND HAVE HAD NO PROBLEMS. YOU JUST NEED TO CHANGE THE FREEZE PLUGS TO BRASS.

I JUST UPGRADED A MARK IV 7.4L AND USED A ZZ502/502 CAM, INTAKE AND ALUMINUM HEADS. I ALSO WENT WITH SRP PISTONS TO UP THE COMP TO 10.7:1 AND PUT A HOLLEY 750 ON IT AND A FULL RETRO FIT TO ROLLER ROCKERS. PROP SHAFT HP IS ESTIMATED AT 505HP.
I HAVE BEEN VERY HAPPY WITH THIS SET UP SO FAR.

ALSO DON'T PLAN ON USING THE STOCK EXHAUST AND KEEP THE TB IGNITION MODULE

hunster

I have found that most of the gm "marinized " crate motors are just truck blocks with corrosion protection! Cam is a street cam , heads aren't the same or close to what merc uses. Unless you can get a build sheet showing what is in the motor you can't really compare the two. Been there done that. You'll spend a lot for that 502 and need a lot of work to get what you want. If you are gonna do the project get a builder such as jc performance , he'll steeer you in the right direction and you won't be sorry.

BY U BOY

CHECK THE CLASSIFIEDS. LOTS OF STUFF TO PONDER
http://www.offshoreonly.com/esvon/page-13127.html

Kidnova

century -

If you are looking into the ZZ502, you might wanna try doing a search re: "ZZ502/502". I've been running one for four seasons now and it's been a very good/dependable engine. I've run mine hard for extended periods with no real issues. There are however a few changes that need to be completed prior to dropping it in a boat. Most are minor and not much $$. Most expensive extras were having Nickerson marinizing the carb, and big oil cooler. Count on bigger oil lines, fittings, etc. as well.


btw... I replaced a 7.4 with my ZZ. The ignition and all marine parts/accessories were transferred over to the ZZ502 with little/no problems.

Shore Thing

Well, good news. After making a few calls I was able to line up a professional engine builder to build me the engine for just a grand more than i was gonna do it for myself. I really thought it would be out of my price range, its a little more than i originally wanted to spend but the price was close enough that I'm willing to pay it for peace of mind. Plus, it sounds like he's gonna give me more hp than I was gonna build for myself.